int10: Don't warn when scanning for devices we don't have.

Some BIOSes (hi XGI!) will attempt to enumerate the PCI bus by asking
for the config space of every possible device number.  This despite
perfectly functional BIOS methods to enumerate the bus exactly.
(cherry picked from commit a57b2f172c)

hw/xfree86/int10/helper_exec.c

@@ -478,15 +478,9 @@ pci_device_for_cfg_address (CARD32 addr)
 
 	struct pci_device_iterator *iter =
 	    pci_slot_match_iterator_create (&slot_match);
+
 	if (iter)
 		dev = pci_device_next(iter);
-	if (!dev) {
-		char buf[128]; /* enough to store "%u@%u" */
-		xf86FormatPciBusNumber(tag >> 16, buf);
-		ErrorF("Failed to find device matching %s:%u:%u\n",
-				buf, slot_match.dev, slot_match.func);
-		return NULL;
-	}
 
 	return dev;
 }